Substituted ureas as sugarcane ripeners

ABSTRACT

Sucrose yield of sugarcane is increased by treating the cane crop a few weeks prior to harvest with a ripening agent comprising a substituted urea.

BACKGROUND OF THE INVENTION

As sugar is among the principal foods for man and animals, as well as a commercially important food for fermentation organisms, much research is being devoted to raising the sucrose yield of sugarcane in a variety of ways. In recent years this research has increasingly turned toward a search for chemical agents which effectively enhance the ripening of sugarcane and do so in a manner which is both safe and economical.

Some of the more successful chemical ripeners for sugarcane so far discovered are disclosed in U.S. Pat. Nos. 3,224,865; 3,245,775; 3,291,592; 3,482,959; 3,482,961; 3,493,361; 3,505,056; 3,660,072 and 3,671,219. Still other chemical agents which have been found successful or shown promise as sugarcane ripeners, such a cyclo-leucine, anisomycin and cycloheximide, are disclosed, for instance, in Hawaiian Planters' Record, Vol. 58, No. 5, pp. 71-79 (1970).

As is evident from these prior disclosures, the more active ripeners differ widely from each other in terms of chemical structure as well as chemical and biological properties. In the search for effective ripeners failures continue to outnumber successes by a wide margin. Moreover, because of toxicological or ecological concerns and the consequent possibility that rotation of use of different chemical ripeners in consecutive seasons in a given area may be preferable to the continued use of a single ripener mixture, the search for new sugarcane ripeners continues unabated.

Generally speaking, chemicals selected for evaluation are those which have been previously found active in work with other plants as plant hormones, hormonal or non-hormonal herbicides, antifungal agents or antibiotics, growth inhibitors or, contrariwise, growth stimulants. However, among the compounds heretofore known to be useful for such other special and often contradictory purposes only an exceptional few are found to be effective in controlling the ripening of sugarcane in the desired manner.

No predictable relationship has yet been recognized between (a) the chemical structure of such compounds, (b) their phytotoxic effects, or (c) their physiological effects on the morphogenetic development of the plant, on the one hand, and their activity in having positive effects on ripening, on the other hand.

OBJECTS OF THE INVENTION

It is an object of this invention to provide a substance which is economically useful as a chemical ripening agent for sugarcane. A more general object is to increase the sucrose yield of sugarcane by chemically treating it during its maturation prior to harvest without introducing objectionable toxicological hazards. More specifically, it is an object of this invention to increase the sucrose yield of maturing sugarcane by treating a cane crop as the end of their normal maturation cycle or their normal harvest date approaches with a relatively inexpensive material which is sufficiently stable to provide the desired effect over a period of several weeks between application and a variable harvest date, but yet has a relatively low degree of persistence and is susceptible to autodecomposition or to decomposition by soil bacteria. A compound which increases the sucrose content only temporarily over a period of three weeks or less after application and then results in a substantial decrease is usually not a desirable chemical ripener except in situations where harvesting time can be rigidly programmed in advance in relation to the time of application of the chemical ripener.

SUMMARY OF THE INVENTION

According to the present invention the desired objectives have been achieved by the application of a ripening composition comprising a substituted urea as hereinafter defined. More specifically, an excellent increase in sucrose yield can be obtained by applying a spray or dust comprising said substituted urea to sugarcane stalks and leaves in a crop which is nearing the normal maturity stage, and harvesting such crops about 2-10 weeks later. The composition is applied directly to the stalks and leaves by spraying, dusting or the like in order that it be deposited on the stalks and leaves including the younger, growing parts thereof. Experimentally, it can be applied by injection into the spindle.

As is well known, the normal maturation cycle of sugarcane can vary considerably depending on local conditions, from less than 1 year to 3 years or more. For instance, under conditions such as those prevailing in Hawaii sugarcane is normally ripe for harvesting when about 18 to 36 months of age while in other areas of the world sugarcane can be only 9 to 12 months of age when harvested.

The preferred usage form is a mixture containing the substituted urea in an aqueous solution or suspension utilizing one or a combination of known surface active agents commonly and variously used in the prior art as wetting agents, detergents or emulsifying agents. However, dry dusting compositions containing the substituted urea and a solid diluent such as clay are also useful.

In accordance with this invention, a sugarcane crop which is nearing the normal maturity stage is treated with a substituted urea as herein defined or with a composition containing same about two to ten weeks before harvest, the preferred time for treatment being between about four and eight weeks prior to harvest.

Good results are obtained when the sugarcane crop is treated at a rate in the range of from 1 to 4 pounds of a substituted urea as herein defined or equivalent substituted urea containing composition per acre of sugarcane. However, higher rates (e.g., up to about 30 pounds of substituted urea or more per acre) or rates lower than 1 pound per acre can also be used. The optimum amount will vary somewhat depending on the particular mode of application, environmental conditions, time of year, and age and variety of cane being treated, but can readily be determined for each particular case by preliminary testing.

The substituted urea is conveniently applied in the field in the form of an aqueous solution, emulsion or suspension, i.e., in a liquid composition which may be sprayed onto the maturing cane plants from a boom-sprayer, or an airplane, or it can be dusted on from an airplane or the like as a dust composition which contains the active compound diluted with an inert solid such as clay.

In preparing suitable liquid composition, surface active agents of the type described, for instance, in U.S. Pat. No. 3,224,865, column 2, lines 61-66 or in U.S. Pat. No. 3,245,775, column 2, lines 57-64 are convenient to use. The preferred surfactants for use in liquid compositions of the present invention are those of the non-ionic type, e.g., alkyl phenoxy poly(ethyleneoxy)ethanols such as adducts of nonylphenol and ethylene oxide; trimethyl nonyl polyethylene glycol ethers; polyethylene oxide adducts of fatty and resin acids, and long chain alkyl mercaptan adducts with ethylene oxide. The surfactant (surface active agent) is not critical.

With the type of spray apparatus used in this work, it has been found convenient to apply the product to the sugarcane field in the form of an aqueous solution, suspension or emulsion having a concentration of active agent such that the application at the rate of from 5 to 20 gallons of liquid composition per acre will provide the required dosage of active chemical. However, the use of lower or higher gallonages may be preferred when a different dispensing mechanism is used.

The preferred carrier for the active ripening agent is water to which about 0.1 to 2 percent by weight of surface active agent has been added. However, instead of using water as the carrier, non-phytotoxic mineral oils either as such or in the form of water-in-oil or oil-in-water emulsions may be used similarly in accordance with practices which are otherwise well known in the art of treating vegetation in the field with beneficial growth control agents. Excellent results are obtained when the substituted urea is present as essentially the sole active ingredient in the treating composition, but it may also be applied in combination with other ripeners.

The substituted ureas as a genus are well known, as well as methods for their synthesis. A typical synthesis starts with the relevant isocyanate. This is reacted with the respective amine to make the desired substituted urea. More detailed procedures for synthesis of the substituted ureas are given in Kirk-Othmer, Encyclopedia of Chemical Technology, 2d Ed., 22, 188 ff.

The substituted ureas are not strangers to agriculture. In the past, however, they have been used exclusively as herbicides (Kirk-Othmer, op. cit.). The success of these materials is considered due to their ability to interfere with photosynthesis. Accordingly, it is surprising that the substituted ureas of this invention not only don't kill the sugarcane plants--they increase the sugar content.

The substituted ureas contemplated for use in this invention are the following:

    __________________________________________________________________________     Log No.                                                                        __________________________________________________________________________     2047                                                                                 ##STR1##                                                                 2071                                                                                 ##STR2##                                                                 2072                                                                                 ##STR3##                                                                 2074                                                                                 ##STR4##                                                                 2105                                                                                 ##STR5##                                                                 2107                                                                                 ##STR6##                                                                 2108                                                                                 ##STR7##                                                                 2109                                                                                 ##STR8##                                                                 2112                                                                                 ##STR9##                                                                 2125                                                                                 ##STR10##                                                                2130                                                                                 ##STR11##                                                                2132                                                                                 ##STR12##                                                                2133                                                                                 ##STR13##                                                                __________________________________________________________________________

FIELD TREATMENT Test Procedure

The following test procedure was used to obtain the data reported in the Table.

A. Sugarcane Plant Selection and Labeling

Prior to establishing testing in the fields used, untreated duplicate samples were taken at 100-ft. intervals over the entire length of the three fields (1320 ft. long). With the exception of definite differences between varieties, there was little variation between stalks over the length of the field. As the season progressed, age of the stalk played a role in ripening readings, strongly suggesting that only immature primaries be worked with or immature secondary stalks be worked with in late testing. This was done.

Three different varieties, selected because of their non-closely related genetics, were all treated with spindle treatments. The three varieties were CL-41-223, CL-54-378 and CL-59-1052. Treatments of all varieties were conducted on the outside two rows for ease of accessibility. Selected stalks were labeled with three colors of plastic tape: red, for the high rate, blue, for the median rate, and green, for the lowest rate. In the spindle tests, three replicate plants were tagged with each color, while in spray tests the beginning and end were identified--about 10 ft. of row. The date of application and treatment code number were indelibly inscribed on the tape.

B. Spindle Treatment

Plants were selected for equal height and size (7-9 leaves), grouped into three treatment rates and replicates of three. The three rates selected for application addition of the substituted urea were 10, 1, and 0.1 mg/plant. The compounds were weighed in the laboratory directly into 20-oz. polyethylene bottles and shipped undiluted to the field. A water solution containing 1% Tween 20 was made up in the lab, shipped to the field, and added in the field. Dilutions used gave 10, 1 and 0.1 mg. per plant when applied in 0.3 ml. Acetone or isopropyl alcohol were used when solubility problems arose. A volume of 0.3 ml. per plant was used. Injections into the spindle were made with either an 18 or 20-gauge needle and a 1.0 cc syringe.

Observations, such as leaf discoloration, injury to foliage or spindle, were made weekly.

C. Foliar Treatment

Compounds were prepared for foliar spraying in the field in the same general way as those used for spindle application. Larger amounts of compound and greater volumes were used to allow spraying. Three rates were used, viz., 8, 2 and 0.5 lbs. active ingredient ("A. I.") per acre. Sixty gallons of spray was found more desirable than 15 or 30 when applied by hand sprayer at 3 mph because the spray droplets were larger and more controllable. Better coverage resulted and spraying was not as easily disrupted or distorted by wind.

Ten feet of row was labeled with tape for each compound, with each treated area separated from another by about four feet. This is idealized, since separation may be 20 feet or more depending on stand quality.

The spray equipment used for making applications included a CO₂ pressure tank and A. I. container on a back pack, plus a spray rig. Prior to spraying, the 330 mls. of compound solution was placed in a 16-oz. plastic container. The bottle cap had two holes cut through it--one to allow a tube to enter and extend to the bottom of the bottle, and the other to allow pressurized gas to enter. A piece of plastic wrap was placed under the cap prior to spraying to prevent spillage. This was pierced when the container was placed into the spray head. The container was placed into the bottom of the stainless steel canister and the retaining cap screwed tightly into place. The CO₂ line from the back pack tank was attached to the canister held on the ammunition belt around the person doing the spraying. When the valve was depressed, CO₂ pressurized the canister and spray emitted from the nozzles. Spraying was accomplished by walking at 3 mph (pre-calibrated), starting several feet before reaching the area to be treated. When the tape marker at the beginning of the plot was passed, the CO₂ valve was actuated and spraying began. Spraying was continued until the container in the canister was empty. Acetone was placed in the container and pressurized to clean the system before spraying the next compound.

D. Evaluation Procedure

Four weeks after application, cane stalks were cut from the field with lopping shears with sufficient length to assure sampling of ten internodes counting back from the growing tip. Generally, cane from six or eight treatments of the highest rate was cut first. Leaves were stripped from the stalk at the point of sampling and carried to the evaluation table. A juice sample was squeezed from the internode tissue sections using a modified pair of pliers (small plates welded to the jaws). The juice was deposited directly onto a hand-held, temperature-compensated, refractometer and the percent soluble solids (Brix) read and recorded. The refractometer was dipped into a beaker of clear water, removed and wiped dry with a paper towel, and thus made ready for the next sample. If the Brix readings from a treatment warranted, the median rate would be evaluated, and likewise, the low rate. Generally, untreated readings were 4.5-5.5, depending on variety.

EXAMPLE 1 (Log 2047 in the Table)

Following the above Test Procedure (spindle application) a substituted urea of the formula ##STR14## was dissolved in water with "Tween-20" surfactant at 10 mg. A. I. per plant, using the three varieties indicated. (Tween 20, a nonionic surfactant, is a polyoxyethylene derivative of the monolaurate ester of sorbitan fatty acid. (It is available commercially from ICI United States, Inc.) After four weeks Brix readings were taken for treated and untreated plants to determine sucrose content as described in the Test Procedure, and the ratio of Brix readings of treated plants to Brix readings for untreated plants determined arithmetically. Obviously, if the ratio exceeds unity, the inference is that the increased sugar (i.e., ripening) was caused by the A. I. The results showed ratios substantially in excess of one on all three varieties. These results, together with others, are reported in the Table. Not all compounds gave improved results for each of the three varieties. However, every one of the compounds showed improved ripening for at least one of the varieties. In the Table the compounds are identified by Log Numbers; see identities, above.

Three well-known commercial ripeners (Roundup, Polaris, and Embark) were tested under similar conditions at 10 mg/plants, and results for them are given.

    ______________________________________                                         Data show the treated/untreated (T/C) ratios which are                         averages of the Brix readings taken from the internodal                        tissues. The ratios give a valid basis of comparison.                                                        Rate (mg/plant)                                  Log Number    Variety.sup.1                                                                           10     1.0       0.1                                    ______________________________________                                         2047          1052     1.936  --        --                                     2071          223      1.692  --        --                                                   378      1.475  1.158     --                                                   223      1.450  --        --                                                   1052     1.574  1.089     --                                                   223      1.158  1.717     1.390                                                378      1.005  1.184     1.548                                  2072          223      1.715  --        --                                                   378      1.473  1.333     --                                                   1052     1.814  1.784     --                                     2074          378      1.389  1.314     --                                     2105          378      2.112  1.462     1.654                                                1052     1.877  1.984     1.846                                  2107          1052     1.634  1.857     --                                     2108          1052     1.709  1.395     --                                     2109          102      2.011  1.977     2.160                                                378      2.002  1.524     1.143                                  2112          1052     1.890  2.148     --                                                   378      1.887  1.697     1.123                                  2125          1052     1.579  1.604     --                                     2130          1052     2.050  1.635     1.639                                  2132          378      1.340  1.604     --                                     2133          378      1.516  1.319     --                                     2002                                                                           (Roundup Standard)                                                                           378      1.404  --        --                                                   1052     2.008  --        --                                                   223      2.356  --        --                                     2061                                                                           (Polaris Standard)                                                                           378      1.219  --        --                                                   1052     0.883  --        --                                                   223      2.312  --        --                                     2062                                                                           (Embark Standard)                                                                            378      1.177  --        --                                                   1052     0.982  --        --                                                   223      1.203                                                   ______________________________________                                          .sup.1 1052 = Cl59-1052 378 = Cl54-378 223 = Cl41-223-                   

Roundup (Log 2002) is understood to be the isopropylamine salt of N-(phosphonomethyl)glycine. Polaris (Log 2061) is understood to be N,N-bis(Phosphonomethyl)glycine. Embark (Log 2062) is understood to be N-[2,4-Dimethyl-5-[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide.

Although the experiments were done by spindle application, the same improvements will be achieved by foliar application, as described in the Test Procedure. For commercial use in the field foliar application would of course be employed.

In commercial operation the A. I. is applied by foliar application, by spraying an aqueous solution or suspension of the substituted urea, at a time from about 2 to 10 weeks prior to harvest, and preferably when the plants are between about 18 and 24 months of age. The aqueous composition preferably contains about 0.6 to 16 wt.% A. I., about 0.1-2 wt.% nonionic surfactant, and is sprayed at the rate of about 5 to 20 gallons of aqueous composition per acre. 

I claim:
 1. A process for modifying the ripening of sugarcane plants so as to increase their yield of sucrose which comprises applying a substituted urea in a sucrose increasing amount directly to the cane plants at a time from about 2-10 weeks prior to harvest; said substituted urea being a member of the group consisting of ##STR15##
 2. Process according to claim 1 in which the substituted urea is ##STR16##
 3. Process according to claim 1 in which the substituted urea is ##STR17##
 4. Process according to claim 1 in which the substituted urea is ##STR18##
 5. Process according to claim 1 in which the substituted urea is ##STR19##
 6. Process according to claim 1 in which the substituted urea is ##STR20##
 7. Process according to claim 1 in which the substituted urea is ##STR21##
 8. Process according to claim 1 in which the substituted urea is ##STR22##
 9. Process according to claim 1 in which the substituted urea is ##STR23##
 10. Process according to claim 1 in which the substituted urea is ##STR24##
 11. Process according to claim 1 in which the substituted urea is ##STR25##
 12. Process according to claim 1 in which the substituted urea is ##STR26##
 13. Process according to claim 1 in which the substituted urea is ##STR27##
 14. Process according to claim 1 in which the substituted urea is ##STR28##
 15. A process according to claim 1 wherein the substituted urea is sprayed onto the cane plants as a liquid composition containing water as a carrier.
 16. A process according to claim 15 wherein the substituted urea is applied to the cane plants as an aqueous solution or suspension at the rate of about 3 to 20 gallons of aqueous composition per acre.
 17. A process according to claim 16 wherein the cane plants are between 18 and 24 months of age when the substituted urea is applied thereto.
 18. A process according to claim 13 wherein the aqueous composition contains about 0.6 to 16 percent weight of an active ingredient.
 19. A process according to claim 15 wherein the aqueous composition contains a surface active agent. 